Instant messaging (IM) is a technology that facilitates real-time text-based communication between two or more participants over computer networks, e.g., the Internet. Although IM typically happens in real-time, some systems allow the sending of messages to people not currently logged on (offline messages), thus removing much of the difference between IM and e-mail.
Many IM services have additional features, such as immediate receipt of acknowledgment, group chatting, conference services (including voice and video), and file transfer. In certain cases, it is possible to save an IM conversation for later reference. In such cases, instant messages are typically logged in a local message history. Logging instant messages may facilitate the ready exchange of unwieldy information like web addresses or document snippets.